Chemical nickel plating methods and systems



June 2l, 1960 P. TALMEY ET AL CHEMICAL NICKEL PLATING METHODS AND SYSTEMS Filed July 2, 1957 3 Sheets-Sheet 1 INVENTOR. Paul Talmey M//ia/n J Ure/lan June 2l, 1960 P. TALMEY ETAL CHEMICAL NICKEL. PLATING METHODS AND SYSTEMS Filed July 2, 1957 3 Sheets-Sheet 2 June 21, 19607 n P. TALMEY ET AL 2,941,902

CHEMICAL NICKEL PLATING METHODS AND SYSTEMS Filed July 2, 1957 3 Sheets-Sheet 3 F/LTER-e/ F 1g 3 f Zia 2lb Z/c l v 23 ABSORB/NG CLARIFY/NG POLISH/,N6 24 UN/T UN/T UNIT IFI-Q4 1k59 INV ENTORS Paul a/mey BY Wil/iam J Cree/1an United States Patent O CHEMICAL NICKEL PLATING METHODS AND SYSTEMS Paul Talmey, Barrington, and William J. Crehan, Hinsdale, Ill., assignors to General American Transportation Corporation, Chicago, Ill., a corporation of New York Filed July 2, 1957, Ser. No. 669,621

23 Claims. (Cl. 117-102) The present invention relates to chemical nickel plating methods and systems; and it is a general object of the invention to provide an improved method and system of the character of that disclosed in U.S. Patent No. 2,658,839, granted on November 10, 1953, to Paul Talmey and William l. Crehan This application is a continuation-in-part of the application of Paul Talmey and William l. Crehan, Serial No. 490,079, led February 23, 1955, now abandoned, and the last-mentioned application is a continuation-impart of the application of Paul Talmey and William J. Crehan, Serial No. 299,784, tiled July 19, 1952, now Patent No. 2,717,218, granted September 6, 1955.

Another object of the invention is to provide an irnproved method of and system for carrying out a chemical nickel plating operation on a large industrial scale, involving the plating of substantial work-pieces, such as railway tank cars, etc.

Another object of the invention is to provide a method of and a system for carrying out an industrial chemical nickel plating operation, involving the continuous circulation of a large volume of aqueous chemical nickel plating solution, and incorporating improved facilities respectively for heating and for cooling the plating solution in two corresponding different stages in its cycle of circulation.

Another object of the invention is to provide a method of and a system for continuous chemical nickel plating, that incorporates improved facilities that respectively effect primary and secondary heating of the circulated plating solution in accordance with two corresponding and entirely different modes that are respectively substantially ideally situated to lowltemperature and to .high-temperature heating of the plating solution in view of its two corresponding and entirely diierent characteristics respectively at low temperature and at high temperature.

A further object of the invention is to provide a method of and a system for continuous chemically nickel plating, that incorporates improved facilities that respectively effect primary and secondary cooling of the circulated plating solution in accordance with two corresponding and entirely diiferent modes that are respectively substantially ideally suited to high temperature and to low temperature cooling of the plating solution in View of its two corresponding and entirely different characteristics respectively at high temperature and at low temperature.

Another object of the invention is to provide a method of and a system for continuous chemical nickel plating, that incorporates improved facilities for continuously regenerating the circulated plating solution while it has a relatively low temperature, and then for continuously ltering the regenerated plating solution while it has a relatively low' temperature, and then for continuously heating the filtered plating solution, whereby this particular sequence of steps is so correlated with respect to the two different sets of characteristics of the plating solution respectively at low temperature and at high tempera- A ice ture that both spontaneous thermal decomposition of the plating solution and stray nickel plating thereby upon the filter structure are greatly minimized and substantially eliminated as normall contingencies in the plating opera'- tion.

A further object of the invention is to provide an -improved method of and system for continuous chemical nickel plating in which the plating solutionis continuously recirculated from a plating tank through a cooler and thence through a filter and then through a heaterand back to the plating tank, wherein the. temperature ofthe plating solution is rapidly reduced in the cooler from an effective plating temperature to an ineffective plating temperature by admixture of the hot platingl solution with cool plating solution, so as to effect quenching of the hot plating solution, and wherein the temperature of the resulting mixture of plating solution is then further reduced in ythe cooler prior to passage therefrom and delivery to the iilter.

A still further object of the invention is to provide an improved method of and system for continuous chemical nickel plating in which both a better heat-balance and a better heat-control are achieved and .maintained than have been previously realized, thereby effecting botha higher eihc'iency of operation and a higher standardmf uniformity of nickel'plating than have been possible heretofore.

Further features of the invention pertain tothe particular arrangemnt of the steps of the method and o f the elements of the system, whereby the abovefou'tlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

Figure l is a diagrammatic illustration of a system for carryingout a continuous chemical nickel plating operation, embodying the present invention, and in which the method thereof may be carried out;

Fig. 2 is another diagrammatic illustration, similar to Fig. l, disclosing a modification of the system and the method, and also embodying the present invention;

ylineS--S in Fig. 4; and

Fig. 6 is an enlarged fragmentary vertical sectional view of the evaporator, taken in the direction of the arrows along the line 6 6 in Fig. 5.

Referring now to Fig. 1 of the drawings, the continu ous chemical nickel plating system there illustrated and .embodying the features of the present invention fundamentally comprise a storage or surge tank l10, a preheater 11, a condenser or final heater 12, a plating tank 13, a flash evaporator or cooler 14, an after-coolerlS, and a regeneration tank 16, and contains a charge of aqueous chemical nickel plating solution of the nickel cation-hypophosphite anion type. The plating solution may be of any well-known type, such, for example, as disclosed in U.S. Patent No. 2,658,842, granted on November l0, 1953, to Gregoire Gutzeit and Ernest I. Ramirez, but preferably the plating solution has the particular composition disclosed in the copending application of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Serial No. 479,088, led December 31, 1954, since NiSO4.6H2O m.p.l

0.08 NaH2Po, m.p.i 0.225 Lactic anion m.p.l 0.30 Propionic anion rn.p.l 0.03 pH 4.6

The lactic anion may be derived from lactic acid, Vsodium lactate, etc., while the propionic anion may be derived from propionic acid, sodium propionate, etc.

`The absolute concentration of hypophosphite anions in the bath is within the approximate range 0.15 to 1.20 moles/liter; the ratio between nickel cations and hypo-. phosphite anions in the bath is within the approximate range 0.25 to 1.60; the absolute concentration of lactic anions in the bath is within the approximate range 0.25 to 0.60 mole/liter; the absolute concentration of propionic anions in the bath is Within the approximate vrange 0.025 to 0.060 mole/liter; and the initial pH of the bath is adjusted within the approximate range 4.0 to 5.6 employing H2504 or NaOH, as required.

This particular platingbath is very advantageous in the continuous chemical nickel plating process, since it possesses a high plating rate, a high phosphite tolerance,

and great stability under the various temperature and other operating conditions encountered in the system.

p Again referring to Fig. l', the continuous plating system further comprises a pump 17 provided with an inlet communicating with a conduit 18 connected to the bottom of the storage tank and an outlet communicat- -ing with a conduit 19. The conduit 19 communicates with a conduit 20 via two parallel passages respectively -including two iilters 21 and 22; the filter 21 may be isolated and removed from the associated` passage after closure of a cooperating pair of valves 23 and 24; and similarly, the iilter 22 may be isolated and removed from the associated passage after closure of a cooperating pair of valves 25 and 26.

The preheater 11 comprises a main heating chamber 27, top and bottom headers 28 and 29, and -a number of tubes 30 extending through the main heating chamber 27 between the headers 28 and 29. The bottom header 29 is connected to the conduit 20 and the top header 28 is connected to a conduit 31. The conduit 31 commu- `nicates via a valve 32 with a conduit 33 connected to the top of the condenser 12; and also the conduit 31 communicates via a valve 34 with a conduit 35 that communicates with the regeneration tank 16. The bottom of thecondenser 12 communicates with a conduit 36 that is connected to the bottom of the plating tank 13; and the top` of the plating tank 13 is provided with an yoverllow hood 37 that communicates with a conduit 38 that is connected to the side of the flash evaporator 14. The bottom of the flash evaporator 14 is connected to a conduit 39 that communicates with the inlet of a pump 40, the outlet Vof the pump 40 communicating with a conduit 41. The after-cooler comprises a main cooling chamber 42,l top and bottom headers 43 Aand 44, and a number of tubes 45 extending through the main cooling chamber 42 between the headers 43 ,and 44. The'bottom header 44 is connected to the conduit 41 and the top header 43 is connected to a conduit 46. The conduit 46 is connected via a valve 47 to a conduit 48 that communicates with the top of the vregeneration tank 16; and yalso the conduit 46 is connected via a valve 49 to a conduit 50 that communicates with the top of the storage tank 10. The bottom of the -regeneration tank 16 communicates with a conduit 51 that isv connected via a valve 52 to a conduit 53 that communicates with the top of the storage tank 10; and

a make-up conduit 54 is connected via a valve 55 to a conduit 56 that communicates with the top of the regeneration tank 16.

Further, the system comprises a steam jet pump or compressor 57 that is provided with a steam inlet connected to a conduit 58, a vapor inlet that is connected to one Aend of a vapor line 59, and a combined steam and vapor discharge outlet that is connected to a conduit 60. A live steam supply pipe 61 is connected via a valve 62 to the conduit 58; and the other end of the vapor line 59 is connected to the top of the flash evaporator 14. The conduit 60 is connected to the top of the main heating chamber 27 of the preheater 11; while the bottom of the main heating chamber 27 is connected to `a conduit 61. In turn, the conduit 61 i's connected to the inlet of a condensate pump 62, the outlet of which is connected to a conduit 63. The conduit 63 is connected via a valve 64 toa conduit 65 that communi Cates withV the top lof the regeneration tank `16; and also the conduit 63 is connected via a valve 66 to a conduit 67 that extends to drain. A live steam conduit 68 is connected via a valve 69 to a conduit 70 that is connected to the top of the main heating chamber 27 0f the preheater 11. A cool water supply pipe 71 is connected via a valve 72 to a conduit 73 that is connected to the ltop of the main cooling chamber 42 of the aftercooler 15; and the bottom of the main cooling chamber 42 is connected to a conduit 74 that extends to drain. Finally, a live steam conduit 75 is connected via a valve 76 to a conduit 77 that is connected to the side of the condenser 12.

Considering now the general mode of operation of the continuous nickel plating system, the portion of the plating solution that is stored in the storage tank 15) normally has a temperature of about 130 F.; while the portion of the plating solution held as a bath in the plating tank 13 has a temperature of about 210 F. The live steam in the live steam supply pipe 75 has a ternperature of about 215 F. and consequently a pressure only slightly in excess of atmospheric pressure; the live steam in the live steam supply pipe 61 has a pressure of p# per square inch and consequently a temperature well above 212 F.; while the live steam in the live steam supply conduit 65 is at any suitable temperature and corresponding pressure for general heating purposes. Of course, the cool water in the cool water supply conduit 71 has a temperature at ambient or below.

In the normal operation of the system, the plating solution is circulated from the bottom of the storage tank 10 by the pump 17 through one or the other of the filters 21 and 22 and thence into the bottom header 29 of the preheater 11, and from the top header 28 of the preheater 11 into the top of the condenser 12. In the tubes 30 of the preheater 11, the plating solution is heated from a temperature of about F. to a temperature of about F., as explained more fully hereinafter. In the condenser 12, live steam is injected directly into the plating solution, whereby it is heated to a temperature of about 210 F., and then delivered into the plating tank 13.

In the plating tank 13, the object to be nickel-plated is immersed in the plating solution throughout an appropriate time interval to effect the plating upon the surface thereof of a nickel coating of the required thickness; and from the overiiow hood 37 of the plating tank 13, the plating solution is conducted into the side of the ash evaporator 14, wherein it is subjected to a subatmospheric pressure so that water vapor is withdrawn therefrom through the vapor line 59. More partcularly, the operation of the jet steam pump or compressor 57 brings about the drawing of a partial vacuum in the asn evaporator 14 through the vapor line 59, whereby the water vapor in the vapor line 59 and the live steam from the live steam conduit 61 are combined in the steam jet pump 57, and the resulting heating iiuid is conducted compos back via the conduit 60 through the main heating chamber 27 in the preheater 11 effecting heating of the plating solution in the tubes 30 of the preheater 11, as previously explained. The heating iiuid mentioned is condensed in the main heating chamber 27 of the preheater 11, and the condensate is then conducted into the conduit 61', from which it is pumped by the pump 62 via the conduit 67 to drain.

More particularly, in the flash evaporator 14, a partial vacuum is drawn corresponding to about l2-14" of Hg; whereby the plating solution therein is cooled by evaporation from about 210 F. to about 180 F.; and from the bottom portion of the flash evaporator 14, the plating solution is circulated by the pump 40 into the bottorn of the bottom header 44 of the after-cooler 15, and thence from the top header 43 of the after-cooler 15 into the conduit 46. From the conduit 46, the plating solution may be conducted either into the top of the regeneration tank 16 or into the top of the storage tank and normally the plating solution is conducted into the top of the regeneration tank 16. In the tubes 45 of the after-cooler 15, the plating solution is cooled from a temperature of about 180 F. to a temperature of about 130 F. From the bottom of the regeneration tank 16, the plating solution is returned back into the top of the storage tank 10 for recirculation.

In the operation of the system, the required preheating of the plating solution in the main chamber 27 of the preheater 11 is effected fundamentally by the heating iluid supplied via the conduit 60; however, additional heating thereof may be eiiected by the steam supplied via the steam conduit 68. As previously noted, the heating fluid supplied via the conduit 60 is derived from the discharge of the steam jet pump 57. The cooling eliect in the main chamber 42 of the after-cooler 15 is derived from the circulation therethrough of cool water from the cool water supply conduit 71,

In the regeneration tank 16, the composition of the plating solution is substantially maintained by regeneration thereof; and more particularly, a suitable nickel cation-containing reagent, a suitable hypophosphte anioncontaining reagent and an alkalizing reagent are added to the plating solution in the regeneration tank 16 from make-up apparatus, not shown. Specically, the addition of the make-up reagents to the plating solution in the regeneration tank 16 is only diagrammatically i1- lustrated by the make-up conduit 54. Preferably the make-up reagents are added continuously to the plating solution in the regeneration tank 16, so as to prevent any substantial departure ofthe composition thereof from the initial composition with respect to nickel cations and hypophosphite anions, and so as to prevent any substantial departure of the pH thereof from the initial value. Of course, there is some phosphite build-up in the plating solution as time proceeds; however, the plating solution has a very high phosphite tolerance, of the order of 1.0 molar, whereby the plating solution may be employed in the system throughout a considerable time interval with the continuation regeneration thereof as described.

'Ihe arrangement, wherein the plating solution is continuously regenerated in the regeneration tank 16, while the plating solution is relatively cool, at a temperature of about 130 F., and the subsequent continuous filtration of the plating solution in one or both of the lters 21 and 22, while the plating solution is still relatively cool, is very advantageous, as it prevents spontaneous decomposition thereof, i.e. the formation of black precipitate therein. Moreover, the continuous iiltration of the plating solution in one or both of the filters 21 and 22, while it is relatively cool, prevents stray nickel plating upon the filter structure, it being understood that there is a tendency for the plating solution to eiiect stray nickel plating upon the iilter structure, as it is forced under pressure through the interstices thereof, notwithstanding the circumstance that the tilter structure is normally formed of material that is not catalytic, such as a suitable porous ceramic material or the like. Specifically, each of the iilters 21 and 22 normally comprises the porous iilter structure or plates mentioned, whereby the suspended solids in the plating solution are removedY therefrom, while the plating solution is relatively cool, thereby removing all such suspended solids that are insoluble at the temperature of about 130 F., and preceding the heating of the plating solution in the preheater 11, wherein at least some of these suspended solids might have a tendency to dissolve at the higher temperature of about 190 F. As a matter of fact, it is these suspended solids, dust, traces of precipitate, etc., that are largely responsible for the spontaneous decomposition of a chemical nickel plating solution in a chemical nickel plating system of the character described. Accordingly, the continuous regeneration followed by the continuous iiltration, both while the plating solution is relatively cool, as described above, comprises an exceedingly important arrangement of steps that is essential to satisfactory operation of an v industrial chemical nickel plating operation, since it is essential that there be eliminated the hazard of spontaneous thermal decomposition of the nickel plating solution, when the plating solution is of such large volume and the apparatus incorporated in the plating system is so extensive.

In the initial warm-up or starting of the chemical nickel plating system, the plating solution may be circulated from the top header 28 of the preheater 11 via the conduit 35 back into the top of the regeneration tank 16 instead of into the top of the condenser 12, and thence from the regeneration tank 16 back into the storage tank 10, and again returned to the bottom header 29 of the preheater 11 after filtering in one or both of the lters 21 and 22. During the initial warm-up of the system, the heat is supplied into the main chamber 27 of the preheater 11 entirely from the steam conduit 68.

After the initial Warm-up of the plating solution in the system, as described above, the valve 34 is closed and the yvalve 32 is opened, whereby the plating solution is conducted from the top header 28 of the preheater 11 into the top of the condenser 12, instead of into the top of the regeneration tank 16. Of course, at this time, operation of the condenser 12 is initiated by opening t-he valve 76; operation of the jet pump 57 is initiated by opening the valve 62; and operation of the after-cooler 15 is initiated by opening the valve 72. Moreover, the valve 55 is opened, so as to bring about the supply of the make-up reagents into the regeneration tank 16; as a matter of fact, the make-up reagents are normally contained in separate vessels so that the supply of each individual reagent to the regeneration tank 16 may be selectively controlled, a preferred arrangement being disclosed in the copending application of Donald E. Metheny, Serial No. 403,590, iiled January 12, 1954.

The primary heating of the plating solution in the preheater 11 of the indirect contact type followed by the secondary heating of the plating solution in the condenser 12 of the direct contact type is very advantageous, as these two heating operations are particularly wellsuited to the characteristics of the plating solution respectively at a relatively low temperature and at a relatively high temperature. Speciiically, in the preheater 11, there is no occasion to boil the plating solution since this preheating step requires only the elevation of the temperature thereof from about F. to about 190 F. On the other hand, in the condenser 12, the final heating of the plating solution must be to a temperature of about 210u F., whereby the heating step involving the injection of the live steam into the plating solution in the condenser 12 is very advantageous, since it insures the heating of all parts of the solution to the required temperature of about 210 F., without the heating of 7A. any part of the solution to the boiling point, somewhat above 212 F.

The primary cooling of the plating solution in the flash evaporator 14 of the direct contact type followed by the secondary cooling of the plating solution in the after-cooler 15 of the indirect contact type is very advantageous, as these two cooling operations are particularly well-suited to the characteristics of the plating solution respectively at a relatively high temperature and at a relatively low temperature. Speciiically, in the ash evaporator 14, the cooling of the plating solution from a temperature of about 210 F., to a temperature of about 180 F. may be accomplished with greatest facility by the withdrawal or evaporation of water vapor therefrom; whereas in the after-cooler 15, the cooling of the plating solution from a temperature of about 180 F. to a temperature of about 130 F. may be most readily achieved employing the cooling coil 45 that is supplied with the readily available source of coolant in the form of cool water.

Turning now to Fig. 2, the modified form of the continuous chemical nickel plating system there illustrated is fundamentally the same as that described above in conjunction with Fig. 1, and the method of Voperation thereof is also essentially the same. More particularly, the continuous nickel plating system of Fig. 2 is designed for a somewhat larger industrial chemical nickel plating operation than is the system of Fig. l; and the system of Fig. 2 fundamentally comprises a storage or surge tank 110, a preheater 111, a condenser or iinal heater 112, a plating tank 113, a primary asn tank 114, a secondary ash tank 180, an after-cooler 115, and a regeneration tank 116. The general arrangement of the elements named above in the system of Fig. 2 (with the exception of the secondary flash evaporator 180) corresponds to that of the element of the system of Fig. 1, previously described; and in the arrangement of the elements of the system of Fig. 2, the secondary ash evaporator 180 is inserted between the primary ash evaporator 114 and the after-cooler 115. Specifically, the bottom of the primary flash tank 114 is connected via a conduit 181 to the upper side of the secondary ash evaporator 180, the conduit 181 including a throttling valve 182 arranged to establish an appropriate pressure difference between the primary ash evaporator 114 and the secondary ash evaporator 180. The bottom of the secondary flash evaporator 180 is connected by the conduit 139 to the inlet of the pump 140, and the outlet of the pump 148 is connected by the conduit 141 to the bottom header of the after-cooler 115, the top header of the after-cooler 115 being connected to the conduit 146 that accommodates the return of the plating solution back to the regeneration tank 116 or to the storage tank 110.

Further, the system of Fig. 2 comprises a barometric jet condenser 183, a circulating pump 184 and a cooling tower 185. The top of the secondary ash evaporator 180 is connected to a vapor line 186 that is also connected to the top of the barometric jet condenser 183; and the bottom of the jet condenser 183 is connected via a conduit 187 to the inlet of a condensate pump 184, the outlet of the pump 184 being connected to a conduit 186. The conduit 186 is connected via a valve 187' to a conduit 188 extending to drain; and also the conduit 186 is connected via a valve 189 to a conduit 190 extending to the top of the cooling tower 185. The bottom of lthe coolingV tower 185 is connected via a conduit 191 to jet stmcture, not shown, provided in the top of the jet condenser 183.

The fundamental operationv of the system of Fig. 2 is the same as that described in conjunction with the system of Fig. l,- as previously noted; however, in this case, the jet pump 157` draws a partial vacuum via the vapor line 159 in the pr-imary iash evaporator 114 corresponding to a pressure of about 12"-14" of Hg; while the barometric jet condenser 183 draws a partial vacuum via lthe vapor line 186 in the secondary iiash evaporator 180 corresponding to a pressure of about 24-25" Hg. Accordingly, the plating solution at a temperature of about 210 F. in the plating tank 113 is cooled to a temperature of about 180 F. in the primary ash evaporator 114;

and the plating solution is further cooled in the secondary flash evaporator 180 to a temperature of about 140 F.; and ultimately the plating solution is further cooled in the after-cooler to a temperature of about F. before it is returned to the regeneration tank 116. Gt course, tbe plating solution is circulated from the regeneration tank 116 into the storage tank 110 and thence via the pump 117 and through one or both of the filters 121 and 122 into the bottom header of the preheater 111, whereby the plating solution is heated from a temperature of about 135 F. to a temperature of about 165 F in the preheater 111 before it is delivered from the top header thereof into the condenser 112. In the condenser 112, the plating solution is heated from a temperature of about F. to a temperature of about 210 F. and is then delivered to the plating tank 113, thereby completing the cycle thereof.

ln the operation of the barometric jet condenser 183, cool water is supplied from the cooling tower 185 into the jet mechanism, not shown, provided in the barometric jet condenser 183 so as to bring about the jet action that draws the water vapor into the top of the barometric jet condenser 183 via the vapor line 186, whereby the vapor is condensed and the condensate accumulates in the bottom of the barometric jet condenser 183. The condensate is withdrawn from the bottom of the jet condenser 183 by the pump 184 and returned back to the top of the cooling tower 185 for cooling and subsequent recirculation back to the jet mechanism, not shown, incorporated in the barometric jet condenser 183. Excess condensate accumulating lin the bottom of the barometric jet condenser 183 is discharged to drain by the pump 184 yvia the conduit 188, as required, by opening the valve 187 for a suitable time interval.

Moreover, it is noted in connection with the plating system of Fig. 2, that the shown jet pump 157 is not essential, as the barometric jet condenser 183 alone is capable of withdrawing the necessary water vapor from the plating solution in secondary flash evaporator and likewise, the after-cooler 115 is not essential, as the barometric jet condenser 183 is capable of drawing such a high vacuum in the secondary ash evaporator 180 thatthe plating solution is adequately cooled in the secondary flash evaporator 188 so that it may be directly returned to the regeneration tank 116. However, the retention of both the steam jet pump 157 and the after-cooler 115 lends maximum flexibility of control to the plating system.

In conjunction with the plating systems of Figs. l and 2, it is noted that the transfer of heat from the ash evaporators 14 and 114 to the preheaters 11 and 111 by circulation of the water vapor that is withdrawn from the plating solution in the ash evaporators 14 and 114 through the preheaters 11 and 111, and without direct Contact with the plating solutions in the main chambers thereof, is very'advantageous, as it prevents the possibility of any precipitate, dust or other catalytic material that might be entrained in the water vapor mentioned from contact with the plating solutions in the main chambers of the preheaters 11 and 111. In other words, the arrangement achieves the desired heat balance and efcient operation, While eliminating the possible hazard of bringing about spontaneous thermal decomposition of the plating solution lin the preheaters 11 and 111.

As previously explained, the fundamental operation of the system of Fig. 2 is substantially the same as that of the System of Fig. 1; however, the heating and cooling arrangements as described above that are incorporated in the system of Fig. 2 are better suited to the circulation of exceedingly large volumes of plating solution in exceedingly large nickel plating systems.

In conjunction with the continuing nickel plating systems of Figs. l and 2, it is pointed out that the plating tanks 13 and 113 may, in fact, comprise the article to be nickel plated, as disclosed in the previously-mentioned Talmey and Crehan application involving the plating of a nickel coating or lining upon the interior of a railway tank car. In this case, the plating tank 13 or 113 would, in fact, comprise the railway tank car body, whereby the circulation of the plating solution therethrough would bring about the plating of the interior of the railway tank car body.

Normally, the elements in the continuous circulating systems that are in Contact with the hot plating solution are formed either of materials that are not catalytic or lined with such materials in order to prevent nickel plating upon the surfaces thereof. Thus, the preheaters 11 and 111 may be formed directly of glass, such, for example, as Pyrex; while it is preferable that the regeneration tanks 16 and 116, the storage tanks 10 and 110, the condensers 12 and 112, the plating tanks 13 and 113, the tiash evaporators 14 and 114 (as well as the ash evaporator 180) and the after-coolers 15 and 115 be formed of steel and lined with a suitable material that is not catalytic, such for example, as glass or a synthetic organic plastic material, so as to prevent the nickel plating thereupon from the circulated plating solution in contact therewith.

It is preferable that the filters 21 and 22 of Fig. 1 and the filters 121 and 122 of Fig. 2 are substantially identical; and the filter 21 is of composite construction as shown in Fig. 3. More particularly, the filter 21 comprises three sections or Units 21a, 2lb and 21C arranged in series relation between the valves 23 and 24 in the order named. The unit 21a comprises an absorbing element and may essentially comprise a mass of activated carbon; the unit 2lb comprises a clarifying element and may essentially comprise a mass of lter aid, such as diatomaceous earth, cellulosic material, etc.; and the unit 21e comprises a polishing element and may essentially comprise a mass of cotton string.

It is preferable that the flash evaporator or cooler 14 of Fig. 1 and the iiash evaporators 1'14 and 180 of Fig. 2 are substantially identical; and the ash evaporator 14 is of a well-known type manufactured by Schutte & Koerting Co. and of the construction as shown in Figs. 4 to 6, inclusive. More particularly, the dash evaporator 14 comprises an upstanding tubular body element 301, and upper and lower substantially dome-shaped headers 302 and 303 respectively closing the upper and lower ends thereof and respectively connected to the Vapor line 59 and to the conduit 39. Arranged within the upstanding tubular body 301 is a chord plate 303 and a bottom plate 304 cooperating to define a chord pocket 30S adjacent toone segment of the tubular body 301, and communieating adjacent the lower portion thereof lwith the conduit 38. Also a plurality of laterally spaced-apart substantially V-shaped channel elements 306 are arranged within the tubular body 301 and in communication at the ends thereofV with the chord pocket 305, the channel elements 306 being disposed in a substantially horizontal plane and extending from the upper edge of the chord plate 303 to the oppositely disposed segment of the tubular body 301, whereby the channel elements 306 are arranged in laterally spaced-apart relation to define elongated slots therebetween.

IIn the operation of the system of Fig. l, the hot plating solution at a temperature of about 210 F. is conducted via the conduit 38 from the overflow hood 37 of the plating tank 13 into the lower portion of the chord pocket 305, filling the chord pocket 305 and causing substantial turbulation of the plating solution contained therein. The vapor line 59 is connected to the steam jet pump 57, as previously explained, whereby a partial vacuum is drawn in the interior of the ash evaporator 14 corresponding to about 12"--14l of Hg, so as to effect flashing or Vaporization of the plating solution at the top of the chord pocket 305 with the result that the incoming plating solution is quickly cooled or quenched as a consequence of the mixing thereof with the previously cooled plating solution in the chord pocket 305. At the top of the chord pocket 305, the plating solution has a temperature of about F. and overliows therefrom into the adjacent ends of the channel elements 306 proceeding therein laterally thereacross and overflowing therefrom and falling therefrom by the action of gravity in curtains onto the bottom header 303, and then iiowing into the conduit 39. The temperature of the plating solution in the descending curtains is further lowered, whereby the temperature of the plating solution conducted into the conduct 39 is about 180 F.

Recapitulating.-The temperature of the hot plating solution in the conduit 38 is quickly reduced in the chord pocket 305 from about 210 F. to about 185 F. as a result of the quenching action notedg'whereby the temperature of the plating solution in the chord pocket 305y is well below the normal plating temperature thereof; and the further coolingv of the plating solution from about 185 F. to about 180 F. in the descending curtains positively insures that the temperature of the plating solution conducted from the flash evaporator 14 into the conduit 39 is well below the normal plating temperature thereof..

Turning to the matter of the character of the article that may be nickel plated by immersion in the plating tanks 13 and 113 of the systems disclosed, it is noted that the article should have a surface that is formed essen-` tially of a catalytic material. The following elements are catalytic for the oxidation of hypophosphite anions' and thus may be directly nickel plated: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following elements may be nickel plated by virtue of the initial displacement deposition of nickel thereon either directly or through a galvanic effect: copper, silver, gold, beryllium, germanium, aluminum,l carbon, vanadium, molybdenum, tungsten, chromium selenium, tellurium and uranium. The following elemen-ts are non-catalytic and may not ordinarily be nickell plated: bismuth, cadmium, tin, lead and zinc. The activity of the catalytic materials varies considerably, and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel and palladium. The chemical nickel plating process is autocatalytic since both the original surface of the body being plated and the nickel metal that is deposited on the surface thereof are catalytic; whereby the reduction of lthe nickel cations to metallic nickel proceeds with the corresponding oxidation of the hypophosphite anions to phosphite anions, the metallic nickel being deposited upon the surface of the body undergoing the plating operation and producing a nickel coating of any desired thickness proportional to the immersion time. Actually the nickel deposit or plating upon the surface of the body comprises an alloy of nickel and phosphorus, containing about 5% to 11% phosphorus by weight. Moreover, the nickel plating upon the surface of the body is considerably harder and more abrasion-resistant than electro-deposited nickel, whereby the resulting article has utility in a great variety of applications.

Further, in conjunction with the plating of an article, it is pointed out that the usual preparation thereof. that is employed in electro-plating processes is normally required. Specitically, the surfaces of a steel article are prepared by mechanical cleaning, degreasing and light pickling. For example, it is suggested that the surfaces of the article be mechanically cleaned to remove any rust and mill scale therefrom, then subjected to a standard degreasing step, and then lightly pickled in a suitable mineral acid, such as hydrochloric acid.

In View of the foregoing, it is apparent that there have been provided a continuous chemical nickel plating systern and method that achieve high eiciency of the continuous nickel plating operation and eliminate (or at i 11 least greatly minimize) the normal hazard of spontaneous decomposition of the plating solution in a large continuous nickel plating system designed for large-scale industrial operation.

While there has Vbeen described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modiiications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A' chemical nickel plating system comprising a reservoir for storing a first portion of an aqueous chemical nickel plating solution at a first relatively low temperature, a plating chamber for holding a second portion .of said solution as a plating bath at a second relatively high temperature, a preheater, a condenser, a flash tank, an aftercooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said flash tank and then through said after-cooler back into said reservoir, means for conducting a heating fluid through said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution Itherein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to effect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing water vapor from said solution in said flash tank in order to effect initial and direct cooling of said solution therein to a temperature intermediate said first and second temperatures, means for discharging to the exterior at least a portion of said water vapor withdrawn from said solution in saidv iiash tank, the quantity-of live steam injected into said solution in said condenser and the quantity of said water vapor withdrawn from said solution in said iiash tank and discharged to the exterior being substantially equal, and means for conducting a cooling uid through said aftercooler and out of contact with said solution therein in order to effect further and indirect cooling of said solution therein substantially to said rst temperature.

2. A chemical nickel plating system comprising a reservoir for storing a rst portion of an aqueous chemical nickel plating solution at a rst relatively low temperature, a plating chamber for holding a second portion of said solution as a plating bath at a second relatively high tem'- perature, a preheater, a condenser, a flash tank, an aftercooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said flash tank and then through said after-cooler back into said reservoir, means for conducting a heating fluid through said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperature, means for injecting live steam into said solution in said condenser in order to effect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing water vapor from said solution in said flash tank in order to effect initial and direct cooling of said solution therein to a temperature intermediate said first and second temperatures, means for conducting said water vapor withdrawn from said solution in said flash tank through said preheater and out of contact with said solution therein in order to effect condensation thereof, `whereby said last-mentioned means constitutes at least a portion of said previously-mentioned means for conducting a heating uid through said preheater, means for discharging to the exterior at least a portion of said condensate from said preheater, the quantity of live steam injected into said solution in said condenser and the quantity of said condensate produced from said water vapor With- 12 drawn from said solution in said flash tank and discharged to the exterior being substantially equal, and means for conducting a cooling fluid through said after-cooler and out of contact with said solution therein in order to effect further and indirect cooling of said solution therein substantially to said first temperature.

3. A chemical nickel plating systemcomprising a reservoir for storing a first portion of `an aqueous chemical nickel plating solution at a first relatively low temperature, a plating chamber for holding a second portion of said solution as a plating bath at a second relatively high temperature, a preheater, a condenser, a flash tank, and after-cooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said flash tank and then through said aftercooler hack into said reservoir, means for conducting a heating fluid through said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to effect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing water vapor from said solution in said ash tank in order to effect initial and direct cooling of said solution therein to `a temperature intermediate said iirst and second temperatures, means for conducting said Water vapor withdrawn from said solution in said flash tank through said preheater and out of contact with said solution therein in order to eifect condensation thereof, whereby said last-mentioned means constitutes at least a portion of said previously-mentioned means for conducting a heating ilud through said preheater, means for returning to said reservoir one portion of said condensate from said preheater, means for discharging to the exterior another portion of said condensate from s-aid preheater, the quantity of live steam injected into said solution in said condenser and the quantity of said condensate produced from said water vapor withdrawn from said solution in said ilash tank and discharged to the exterior being substantially equal, and means for conducting a cooling fluid through said aftercooler and out of contact with said solution therein in order to effect further and indirect cooling of said solution therein substantially to said first temperature.

4. A chemical nickel plating system comprising a reservoir for storing a first portion of `an aqueous chemical nickel plating solution at a first relatively low temperature, a plating chamber for holding a second portion of said solution as a plating bath at a second relatively high temperature, a preheater, a condenser, a ash tank, an after-cooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said flash tank and then throu-gh said after-cooler4 back into said reservoir, means for conducting a heating fluid through said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to elfect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing Water vapor from said solution in said flash tank in order lto effect initial and direct cooling of said solution therein to a temperature inter-mediate said first and second temperatures, means for conducting said water vapor withdrawn from said solution in said flash tank through said preheater and out of contact with said solution therein in order to effect condensation thereof, additional means for conducting an independent heating medium through said preheater and out of contact with said solution therein, whereby said last-two-mentioned means constitute said previously-mentioned means for conducting a heating uid through said preheater, means for discharging to the exterior at least a portion of said condensate from said preheater, the quantity of live steam injected into said solution in said condenser and the quantity of said condensate produced from said water vapor withdrawn from said solution in said flash tank and discharged to the exterior being substantially equal, and means for conducting a cooling fluid through said after-cooler and out of contact with said solution therein in order to effect further Iand indirect cooling of said solution therein substantially to said first temperature.

5. A chemical nickel plating system comprising a reservoir for storing a first portion of an aqueous chemical nickel plating solution at a first relatively lo-w temperature, a plating chamber for holding a second portion of said solution as a plating ybath at a second relatively high temperature, a preheater, a condenser, a flash tank, an after-cooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said flash tank and then through said aftercooler back into said reservoir, means for conducting a heating fluid through said preheater and out of contact with said solution therein in order to eiiect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to effect further and direct heating of said solution therein substantially to said second temperature, al steam jet pump, means for supplying live steam to said steam jet pump, means including said steam jet pump for withdrawing water vapor from said solution in said flash tank in order to effect initial and direct cooling of said solution therein to a temperature intermediate said first and second temperatures, means for combining the steam discharged from said steam jet pump and said water vapor Withdrawn from said solution in said flash tank and for conducting said combined steam and water vapor through said preheater and out of contact with said solution therein in order to effect condensation thereof, whereby said last-mentioned means constitutes at least a portion of said previously-mentioned means for conducting a heating uid through said preheater, means for discharging to the exterior at least a portion of said condensate from said preheater, the quantity of live steam injected into said solution in said condenser and the quantity of said condensate produced from said water vapor withdrawn from said solution in said flash tank and discharged to the exterior being substantially equal, and means for conducting a cooling uid through said aftercooler and out of contact with said solution therein in order to effect further and indirect cooling of said solution therein substantially to said first temperature.

6. A chemical nickel plating system comprising a reservoir for storing a iirst portion of an aqueous chemical nickel plating solution at a first relatively low temperature, a plating chamber for holding a second portion of said solution as a plating bath at a second relatively high temperature, 1a preheater, a condenser, a first flash tank, a second fiash tank, an after-cooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said first and second flash tanks in series relation and then through said after-cooler back into said reservoir, means for conducting a heating uid through said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to elect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing water vapor from s-aid solution in said first flash tank in order to effect initial and direct cooling of said solution therein to a third temperature disposed below said second temperature, means for conducting said water vapor withdrawn from said first flash ltank through said preheater and out of contact with said solution therein in order to condense said 4last-mentioned water vapor, whereby said last-mentioned means constitutes at least a portion of said previously-mentioned means for conducting a heating fluid through said preheater, means for discharging to the exterior at least a portion of said condensate from said preheater, means for withdrawing water vapor from said solution in said second flash tank in order to effect further and direct cooling of said solution therein to a fourth temperature disposed below said third temperature, means for discharging to the exterior said water vapor withdrawn from said solution in said second flash tank, the quantity of live steam injected into said solution in said condenser and the total quantity of said condensate produced from said water vapor withdrawn from said solution in said first flash tank and said water vapor withdrawn from said solution in said second flash tank. and discharged to the exterior being substantially equal, and means for conducting a cooling iuid through said after-cooler and out of contact with said solution therein in order to effect still further and indirect cooling of said solution therein substantially to said first temperature.

7. A chemical nickel plating system comprising a reservoir for storing a first portion of an aqueous chemical nickel plating solution at a first relatively low temperature, a plating chamber for holding a second portion of said solution as a plating bath at a second relatively high temperature, a preheater, a condenser, a first flash tank, a second flash tank, an after-cooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber andv therefrom. through said-first and second flash tanks in series relation and then through said aftercooler back into said reservoir, means for conducting a heating fluid through-said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to effect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing water vapor from said solution in said rst flash tank in order to effect initial and Vdirect cooling of said solution therein to a third temperature disposed below said second temperature, means for conductingvsaid water vapor withdrawn from said first flash tank through said preheater and out of contact with said solution therein in order to condense Asaid last-mentioned water vapor, whereby said last-mentioned means constitutes at least a portion of said previously-mentioned means for conducting a heating Huid through said preheater, means for returning to said reservoir one portion of said condensate from said preheater, means for discharging to the exterior another portion of said condensate from said preheater, means for withdrawing water 4vapor from said solution in said second flash tank in order to effect further and direct cooling of said solution therein to a fourth temperature disposed below said third temperature, means for discharging to the exterior said water vapor withdrawn from said solution in said second flash tank, the quantity of live steam injectc'd into said solution in said condenser and the total quantity of said condensate produced from said water vapor withdrawn from said solution in said first flash tank and said water vapor withdrawn from said solution in said second flash tank and discharged to the exterior being substantially equal, and means for conducting a cooling lluid through said after-cooler and out of contact with said solution therein in order to eliect still further and indirect cooling of said solution therein substantially to said first temperature.

8. Achemical nickel plating system comprising a reservoir for storing a first portion of an aqueous chemical nickel plating solution at a first relatively low temperature, a plating chamber for holding a second portion of said solution as a plating bath at a second relatively high temperature, a preheater, a condenser, a ash tank, an after-cooler, means for circulating said solution from said reservoir through said preheater and then through said condenser into said plating chamber and therefrom through said flash tank and then through said aftercooler back into said reservoir, means for conducting a heating fluid through said preheater and out of contact with said solution therein in order to effect initial and indirect heating of said solution therein to a temperature intermediate said first and second temperatures, means for injecting live steam into said solution in said condenser in order to effect further and direct heating of said solution therein substantially to said second temperature, means for withdrawing water vapor from said solution in said flash tank in order to effect initial, and direct cooling of said solution therein to a temperature intermediate said first and second temperatures, a barometric jet condensing apparatus, means for conducting to said apparatus said water vapor withdrawn from said solution in said ash tank, the quantity of live steam injected into said solution in said condenser and the quantity of said water vapor withdrawn from said solution in said flash tank and conducted to said apparatus being substantially equal, means for supplying a coolant to said apparatus in order to effect the condensation of said Water vapor conducted thereto, means for discharging said coolant and said condensate from said apparatus to the exteor, and means for conducting a cooling fluid through said after-cooler and out of contact with said solution therein in order to effect further and indirect cooling of said solution therein substantially to said rst temperature.

9. Apparatus for chemical reduction plating operations, said apparatus comprising a container for plating solution, a cooler, a filter, a heater, and means for circulating the plating solution from said container through said cooler and then through said filter and then through said heater and thence back to said container, whereby the plating solution is cooled prior to filtering thereof and is heated subsequent to filtering thereof.

10. The apparatus set forth in claim 9, wherein said filter essentially comprises a mass of activated carbon.

ll. Apparatus for chemical reduction nickel plating operations, said apparatus comprising a container for nickel plating solution, a cooler, a filter, a heater, means for circulating the plating solution from said container through said cooler and then through said filter and then through said heater and thence back -to said container, whereby the plating solution is cooled prior to filtering thereof and is heated subsequent to filtering thereof, and means for supplying a nickel salt to the circulated plating solution between said cooler and said filter so as to replenish the nickel ion content thereof while the plating solution is cool and prior to filtering thereof.

l2. Apparatus for chemical reduction plating operations, said apparatus comprising a container for hot plating solution, means for withdrawing hot plating solution from said container and for mixing the same with previously cooled plating solution and for further cooling the resulting plating solution, a filter, a heater, means for conducting at least a portion of the thus further cooled resulting plating solution through said filter into said heater, and means for supplying hot plating solution from said heater to said container, whereby the plating solution is cooled prior to filtering thereof and is heated subsequent to filtering thereof.

13. The method of chemically plating with nickel a solid body of catalytic material employing an aqueous chemical nickel plating solution of the nickel cationhypophosphite anion type having substantially a predetermined composition and characterized by stability and a low plating rate at aV temperature within a first given rangedisposed well below the boiling point thereof and by instability and a high plating rate at a temperature within a second given range disposed near the boiling point thereof; said method comprising providing a solution as specified, storing a first portion of said solution in a reservoir at a temperature within said first range, holding a second portion of said solution as a plating bath in a plating chamber at a temperature within said second range, circulating said solution from said reservoirAthrough a preheater and a condenser in series relation into said plating chamber and therefrom through a flash tank and an after-cooler in series relation back into said reservoir, indirectly heating said solution in said preheater to a temperature intermediate said first and second ranges, said last-mentioned step involving passing a heating uid through said preheater in heat exchange relationwith said solution, but out of contact therewith, injecting suiiicient live steam into said solution in said condenser directly to heat it to a temperature within said second range, withdrawing sufficient water vapor from said solution in said flash tank directly to cool it to a temperature intermediate said iirst and second ranges, said last-mentioned step involving subjecting said solution to a subatmospheric pressure in said flash tank, indirectly cooling said solution in said after-cooler to a temperature within said first range, said last-mentioned step involving passing a cooling fluid through said after-cooler in heat exchange relation with said solution but out of contact therewith, the quantity of said live steam injected into said solution in said condenser and the quantity of said water vapor withdrawn from said solution in said flash tank being substantially equal, and immersing said body in said bath in said plating chamber.

14. The method set forth in claim 13, wherein the quantity of heat supplied to said solution in said preheater is greater than that supplied thereto in said con` denser.

15. The method set forth in claim 13, wherein the quantity of heat extracted from said solution in said aftercooler is greater than that extracted therefrom in said 'ash tank.

16. The method set forth in claim 13, wherein said circulation of said solution is substantially continuous, said first temperature range extends down to about 'u F., said second temperature range extends up to about 2.10 F., said solution is heated in said preheater to a temperature in the approximate range 165 F. to 190 F., and said solution is cooled in said flash tank to a tem perature in the approximate range F. to 180 F.

17. The method of chemically plating with nickel a solid body of catalytic material employing an aqueous chemical nickel plating solution of the nickel cationhypophosphite anion type having substantially a predetermined composition and characterized by stability and a low plating rate at a temperature within a first given range disposed well below the boiling point thereof and by instability and a high plating rate at a temperature within a second given range disposed near the boiling point thereof; said method comprising providing a solution as specified, storing a first portion of said solution in a reservoir at a temperature within said first range, holding a second portion of said solution as a plating bath in a plating chamber at a temperature within said second range, continuous circulating said solution from said reservoir into said plating chamber and therefrom back into said reservoir, continuously filtering said solution after the withdrawal thereof from said reservoir and while the temperature thereof is within said first range, said last-mentioned step consisting essentially of continuously forcing said solution under pressure through the interstices of filter structure formed of material that is not catalytic, continuously heating said solution lafter said filtration thereof and before the introduction thereof into said plating chamber to a temperature within said second range, continuously cooling said solution after the withdrawal thereof from said plating chamber and before the return thereof back into said reservoir, immersing said body in said second portion of said solu- `tion in said plating chamber to effect nickel plating on the surface of said body, and maintaining substantially said predetermined composition of said second portion of said solution in said plating chamber by continuously regenerating said first portion of said solution in said reservoir, said last-mentioned step consisting essentially of continuously adding to said first portion of said solution in said reservoir appropriate amounts of soluble nickelcontaining and hypophosphite-containing reagents, whereby said continuous filtration of said solution following said continuous regeneration thereof and preceding said continuous heating thereof insures the continuous removal therefrom of any solids suspended therein that are insoluble at the tempearture thereof within said first range so as continuously to eliminate from said solution these suspended solids therein that are largely responsible for undesirable spontaneous decomposition thereof while greatly minimizing the tendency of said solution to effect stray nickel plating upon said filter structure employed in said continuous filtration thereof.

18. The method set forth in claim 17, wherein said rst temperature range extends down to about 130 F., alcosid second temperature range extends up to about 19. The method of chemically plating with nickel a solid body of catalytic material employing an aqueous chemical nickel plating solution of the nickel cation-hypophosphite anion type having substantially a predetermined composition and characterized by stability and a low plating rate at a temperature within a first given range disposed well below the `boiling point thereof and by instability and a high plating rate at a temperature within a second given range disposed near the boiling point thereof; said method comprising providing a solution as specified, storing a first portion of said solution in a reservoir at a temperature within said first range, holding a second portion of said solution `as a plating bath in a plating chamber at a temperature within said second range, continuously withdrawing said solution from said reservoir, continuously filtering said solution after the withdrawal thereof from said reservoir and while the temperature thereof is within said first range, said lastmentioned step consisting essentially of 'continuously forcing said solution under pressure through the interstices of filter structure formed of material that is not catalytic, continuously heating said solution after said filtration thereof to a temperature within said second range, said last-mentioned step including injecting live steam into said solution, continuously introducing said solution into said plating chamber after said heating thereof, continuously withdrawing said solution from said plating Icharnber, continuously Vcooling said solution after the withdrawal thereof from said plating chamber to a temperature within said first range, said last-mentioned step including withdrawing water vapor from said solution, continuously returning said solution to said reservoir after said cooling thereof, immersing said body in said second portion of said solution in said plating chamber to effect nickel plating on the surface of said body, and maintaining substantially said predetermined composition of said second portion o-fsaid solution in said plating chamber by continuously regenerating said first portion of said solution in said reservoir, said last-mentioned step consisting essentially continuously adding to said first portion of said solution in said reservoir appropriate amounts of soluble nickel-containing and hypophosphite-containing reagents, whereby said continuous filtration of said solution following said continuous regeneration thereof and preceding said continuous heating thereof insures the continuous removal therefrom of any solids suspended therein that are insoluble at the temperature thereof within said first range so as continuously to eliminate from said solution these suspended solids therein that are largely responsible for undesirable spontaneous decomposition thereof while greatly minimizing the tendency of said solution to effect stray nickel plating upon said filter structure employed in said continuous filtration thereof.

20. A method of depositing a metal from a chemical reduction type plating bath, said method comprising the steps of immersing an article lto be coated into said plating bath which is maintained at an elevated temperature and is continuously recirculated through a filter, said plating bath being rapidly cooled `before it enters said filter in order to preclude the plating reaction in said filter.

2l. A method of depositing a metal from a chemical reduction type plating bath, said method comprising the steps of immersing an article to be coated into said plating bath which is maintained at an elevated temperature and is continuously recirculated through a filter, said plating bath being rapidly cooled prior to passage thereof through said filter by mixture therewith of previously cooled plating solution in order to preclude the plating reaction in said filter.

22. In the deposition of nickel from a hot chemical reduction plating bath of the type comprising an aqueous solution of at least one nickel salt and a reducing agent in which said solution is continuously recirculated through a filter to thereby remove harmful impurities, the improvement which consists of precluding nickel deposition throughout the filter and associated apparatus as the plating solution circulates therethrough by passing the hot plating solution through a heat. exchanger to cause said solution to cool, a portion of the cool plating solution previously cooled in said heat exchanger being mixed with the hot plating solution after it is Withdrawn from said bath to thereby rapidly reduce the solution temperature below that temperature at which plating occurs.

23. A method of depositing a metal from a chemical reduction type plating bath, said method comprising the steps of immersing an article to be coated into said plating bath maintained at an elevated temperature and contained in a plating tank, continuously recirculating said plating bath from said plating tank through a filter and back to said plating tank, cooling said plating bath from said elevated temperature to a lower temperature after removal thereof from said plating tank Iand prior to passage thereof through said filter in order to preclude the plating reaction in said filter, and heating said plating bath from said lower temperature to said elevated temperature after passage thereof through said filter and prior to return thereof to said plating tank.

References Cited in the file of this patent UNITED STATES PATENTS 2,791,516 Chambers et al. May 7, 1957 

13. THE METHOD OF CHEMICALLY PLANTING WITH NICKEL A SOLID BODY OF CATALYTIC MATERIAL EMPLOYING AN AQUEOUS CHEMICAL NICKEL PLANTING SOLUTION OF THE NICKEL CATIONHYPOPHOSPHITE ANION TYPE HAVING SUBSTANTIALLY A PREDETERMINED COMPOSITION AND CHARACTERIZED BY STABILITY AND A LOW PLANTING RATE AT A TEMPERATURE WITHIN A FIRST GIVEN RANGE DISPOSED WELL BELOW THE BOILING POINT THEREOF AND BY INSTABILITY AND A HIGH PLATING RATE AT A TEMPERATURE WITHIN A SECOND GIVEN RANGE DISPOSED NEAR THE BOILING POINT THEREOF, SAID METHOD COMPRISING PROVIDING A SOLUTIO AS SPECIFIED, STORING A FIRST PORTION OF SAID SOLUTION IN A RESERVOIR AT A TEMPERATURE WITHIN SAID FIRST RANGE, HOLDING A SECOND PORTION OF SAID SOLUTION AS A PLANTING BATH IN A PLATING CHAMBER AT A TEMPERATURE WITHIN SAID SECOND RANGE, CIRCULATING SAID SOLUTION FROM SAID RESERVOIR THROUGH A PREHEATER AND A CONDENSER IN SERIES RELATION INTO PLATING CHAMBER AND THEREFROM THROUGH A FLASH TANK AND AN AFTER-COOLER IN SERIES RELATION BACK-INTO SAID RESERVOIR, INDIRECTLY HEATIG SAID SOLUTION IN SAID PREHEATER TO A TEMPERATURE INTERMEDIATE SAID FIRST AND SECOND RANGES, SAID LAST-MENTIONED STEP INVOLVING PASSING A HEATING FLUID THROUGH SAID PREHEATER IN HEAT EXCHANGE RELATION WITH SAID SOLUTION, BUT OUT OF CONTACT THEREWITH, CONDENSER DRIRECTLY TO HEAT IT TO ATEMPERATURE WITHIN SAID CONDENSER DIRECTLY TO HEAT IT TO A TEMPERATURE WITHIN SAID SECOND RANGE, WITHDRAWING SUFFICIENT WATER VAPOR FROM SAID SOLUTION IN SAID FLASH TANK DIRECTLY TO COOL IT TO A TEMPERATURE INTERMEDIATE SAID FIRST AND SECOND RANGES, SAID LAST-MENTIONED STEP INVOLVING SUBJECTING SAID SOLUTION TO A SUBATMOSPHERIC PRESSURE IN SAID FLASH TANK,INDIRECTLY COOLING SAID SOLUTION IN SAID AFTER-COOLER TO A TEMPERATURE WATER VAPOR WITHDRAW FROM SAID SOLUTION IN SAID FLASH PASSING A COOLING FLUID THROUGH SAID AFTER-COOLER IN HEAT EXCHANGE RELATION WITH SAID SOLUTION BUT OUT OF CONTACT THEREWITH, THE QUANTITY OF SAID LIVE STEAM INJECTED INTO SAID SOLUTION IN SAID CONDENSER AND THE QUANTITY OF SAID WATER VAPOR WITHDRAW FROM SAID SOLUTION IN SAID FLASH TANK BEING SUBSTANTIALLY EQUAL, AND IMMERSING SAID BODY IN SAID BATH IN SAID PLATING CHAMBER.
 20. A METHOD OF DEPOSITING A METAL FROM A CHEMICAL REDUCTION TYPE PLATING BATH, SAID METHOD COMPRISING THE STEPS OF IMMERSING AN ARTICLE TO BE COATED INTO SAID PLATING BATH WHICH IS MAINTAINED AT AN ENVATED TEMPERATURE AND IS CONTINUOUSLY RECIRCULATED THROUGH A FILTER, SAID PLATING BATH BEING RAPIDLY COOLED BEFORE IT ENTERS SAID 